The invention relates to computer system recovery from an undesirable condition and in particular to restarting the computer system with minimal need for logical file rebuilding.
In a computer system which uses logical files such as directories to index large amounts of data, a system failure, such as loss of power, or auxiliary storage failure, can result in the logical files being in an unknown condition. Past solutions to this problem have involved rebuilding the logical files from the data. This solution has involved a great deal of time to return the system to operation because of all the data needed to be read to regenerate the logical files. A further solution has involved the use of journaling transactions. This solution added overhead on I/O (Input/Output) operations and generally adversely affected performance of the system.
Individual jobs running on the system have made use of job checkpoint/restart marking to cause a job to stop at a predetermined point prior to updating logical files. This resulted in the logical file related to the job to be in a known condition at all times. Recovery was then easy for that particular job. Other jobs not so marked by their owners were not so fortunate. The individual checkpoint/restart was always present, so overall performance was affected during normal operation of the system.